From 4b25f2d139c1647c76950a384846cbe9249a3764 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tao=20Bojl=C3=A9n?= <git@btao.org>
Date: Sat, 4 Jul 2026 12:46:42 +0100
Subject: [PATCH] fix: harden Haraka TLS (renegotiation DoS + untrusted cert
 chain)

Two scanner findings on app.shroud.email:25, both in the SMTP (Haraka)
TLS path:

1. Client-initiated TLS renegotiation allowed (DoS). Haraka tls_socket
   passes secureOptions from tls.ini [main] straight to
   tls.createSecureContext. Set secureOptions=1073741824
   (crypto.constants.SSL_OP_NO_RENEGOTIATION) to refuse renegotiation,
   closing the CPU-exhaustion vector.

2. Untrusted certificate presented on port 25. The daily cron bundle
   appended a hardcoded, now-expired intermediate (lets-encrypt-r4.pem,
   expired 2025-09-15) to Caddy fullchain, producing a broken chain.
   Caddy {domain}.crt is already leaf + intermediates; copy it verbatim
   and drop the stale intermediate. Also run the bundle at container
   startup (not only daily) so a fresh pem_certs volume is populated
   before Haraka first STARTTLS, and no-op gracefully when Caddy has not
   issued yet.
---
 cron/Dockerfile                     | 10 +++++-----
 cron/bundle_certs.sh                | 19 +++++++++++++-----
 cron/lets-encrypt-r4.pem            | 30 -----------------------------
 haraka/haraka_config/config/tls.ini |  5 +++++
 4 files changed, 24 insertions(+), 40 deletions(-)
 delete mode 100644 cron/lets-encrypt-r4.pem

diff --git a/cron/Dockerfile b/cron/Dockerfile
index 2c0a5db..cfa6a26 100644
--- a/cron/Dockerfile
+++ b/cron/Dockerfile
@@ -5,11 +5,11 @@ RUN apk update && \
 
 WORKDIR /workdir
 
-COPY lets-encrypt-r4.pem /workdir/lets-encrypt-r4.pem
-COPY bundle_certs.sh /etc/periodic/daily/bundle_certs
-
-RUN chmod +x /etc/periodic/daily/bundle_certs
+COPY bundle_certs.sh /usr/local/bin/bundle_certs
+RUN chmod +x /usr/local/bin/bundle_certs
 
 VOLUME /pem
 
-CMD ["crond", "-f", "-l", "0"]
+# Run bundle once at boot (populate pem_certs before Haraka's first STARTTLS),
+# then keep the daily crond for renewals. Caddy's fullchain is copied verbatim.
+CMD ["sh", "-c", "bundle_certs; exec crond -f -l 0"]
diff --git a/cron/bundle_certs.sh b/cron/bundle_certs.sh
index 02e3cc8..917d72c 100644
--- a/cron/bundle_certs.sh
+++ b/cron/bundle_certs.sh
@@ -3,9 +3,18 @@ set -e
 
 if [ -z "$EMAIL_DOMAIN" ]; then echo "EMAIL_DOMAIN is not set"; exit 1; fi
 
-cd /workdir
+CERT_DIR="/caddy/certificates/acme-v02.api.letsencrypt.org-directory/$EMAIL_DOMAIN"
+LEAF="$CERT_DIR/${EMAIL_DOMAIN}.crt"
+KEY="$CERT_DIR/${EMAIL_DOMAIN}.key"
+
+if [ ! -s "$LEAF" ] || [ ! -s "$KEY" ]; then
+  echo "Caddy cert not ready yet ($LEAF); skipping"
+  exit 0
+fi
+
 echo "Copying Caddy certs to Haraka..."
-cd "/caddy/certificates/acme-v02.api.letsencrypt.org-directory/$EMAIL_DOMAIN"
-cp "${EMAIL_DOMAIN}.key" /pem/tls_key.pem
-cat "${EMAIL_DOMAIN}.crt" /workdir/lets-encrypt-r4.pem > /pem/tls_cert.pem
-echo "Copied Caddy certs to Haraka."
\ No newline at end of file
+# Caddy's {domain}.crt is already the full chain (leaf + intermediates).
+# Copy it verbatim — appending a separate intermediate would duplicate/break the chain.
+cp "$KEY" /pem/tls_key.pem
+cp "$LEAF" /pem/tls_cert.pem
+echo "Copied Caddy certs to Haraka."
diff --git a/cron/lets-encrypt-r4.pem b/cron/lets-encrypt-r4.pem
deleted file mode 100644
index 578b3bd..0000000
--- a/cron/lets-encrypt-r4.pem
+++ /dev/null
@@ -1,30 +0,0 @@
------BEGIN CERTIFICATE-----
-MIIFFjCCAv6gAwIBAgIRAIp5IlCr5SxSbO7Pf8lC3WIwDQYJKoZIhvcNAQELBQAw
-TzELMAkGA1UEBhMCVVMxKTAnBgNVBAoTIEludGVybmV0IFNlY3VyaXR5IFJlc2Vh
-cmNoIEdyb3VwMRUwEwYDVQQDEwxJU1JHIFJvb3QgWDEwHhcNMjAwOTA0MDAwMDAw
-WhcNMjUwOTE1MTYwMDAwWjAyMQswCQYDVQQGEwJVUzEWMBQGA1UEChMNTGV0J3Mg
-RW5jcnlwdDELMAkGA1UEAxMCUjQwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEK
-AoIBAQCzKNx3KdPnkb7ztwoAx/vyVQslImNTNq/pCCDfDa8oPs3Gq1e2naQlGaXS
-Mm1Jpgi5xy+hm5PFIEBrhDEgoo4wYCVg79kaiT8faXGy2uo/c0HEkG9m/X2eWNh3
-z81ZdUTJoQp7nz8bDjpmb7Z1z4vLr53AcMX/0oIKr13N4uichZSk5gA16H5OOYHH
-IYlgd+odlvKLg3tHxG0ywFJ+Ix5FtXHuo+8XwgOpk4nd9Z/buvHa4H6Xh3GBHhqC
-VuQ+fBiiCOUWX6j6qOBIUU0YFKAMo+W2yrO1VRJrcsdafzuM+efZ0Y4STTMzAyrx
-E+FCPMIuWWAubeAHRzNl39Jnyk2FAgMBAAGjggEIMIIBBDAOBgNVHQ8BAf8EBAMC
-AYYwHQYDVR0lBBYwFAYIKwYBBQUHAwIGCCsGAQUFBwMBMBIGA1UdEwEB/wQIMAYB
-Af8CAQAwHQYDVR0OBBYEFDadPuCxQPYnLHy/jZ0xivZUpkYmMB8GA1UdIwQYMBaA
-FHm0WeZ7tuXkAXOACIjIGlj26ZtuMDIGCCsGAQUFBwEBBCYwJDAiBggrBgEFBQcw
-AoYWaHR0cDovL3gxLmkubGVuY3Iub3JnLzAnBgNVHR8EIDAeMBygGqAYhhZodHRw
-Oi8veDEuYy5sZW5jci5vcmcvMCIGA1UdIAQbMBkwCAYGZ4EMAQIBMA0GCysGAQQB
-gt8TAQEBMA0GCSqGSIb3DQEBCwUAA4ICAQCJbu5CalWO+H+Az0lmIG14DXmlYHQE
-k26umjuCyioWs2icOlZznPTcZvbfq02YPHGTCu3ctggVDULJ+fwOxKekzIqeyLNk
-p8dyFwSAr23DYBIVeXDpxHhShvv0MLJzqqDFBTHYe1X5X2Y7oogy+UDJxV2N24/g
-Z8lxG4Vr2/VEfUOrw4Tosl5Z+1uzOdvTyBcxD/E5rGgTLczmulctHy3IMTmdTFr0
-FnU0/HMQoquWQuODhFqzMqNcsdbjANUBwOEQrKI8Sy6+b84kHP7PtO+S4Ik8R2k7
-ZeMlE1JmxBi/PZU860YlwT8/qOYToCHVyDjhv8qutbf2QnUl3SV86th2I1QQE14s
-0y7CdAHcHkw3sAEeYGkwCA74MO+VFtnYbf9B2JBOhyyWb5087rGzitu5MTAW41X9
-DwTeXEg+a24tAeht+Y1MionHUwa4j7FB/trN3Fnb/r90+4P66ZETVIEcjseUSMHO
-w6yqv10/H/dw/8r2EDUincBBX3o9DL3SadqragkKy96HtMiLcqMMGAPm0gti1b6f
-bnvOdr0mrIVIKX5nzOeGZORaYLoSD4C8qvFT7U+Um6DMo36cVDNsPmkF575/s3C2
-CxGiCPQqVxPgfNSh+2CPd2Xv04lNeuw6gG89DlOhHuoFKRlmPnom+gwqhz3ZXMfz
-TfmvjrBokzCICA==
------END CERTIFICATE-----
diff --git a/haraka/haraka_config/config/tls.ini b/haraka/haraka_config/config/tls.ini
index 15041fb..48b41d7 100644
--- a/haraka/haraka_config/config/tls.ini
+++ b/haraka/haraka_config/config/tls.ini
@@ -1,2 +1,7 @@
 key=certs/tls_key.pem
 cert=certs/tls_cert.pem
+
+; Disable client-initiated TLS renegotiation (DoS via repeated handshakes).
+; Value is crypto.constants.SSL_OP_NO_RENEGOTIATION (0x40000000), passed
+; through to tls.createSecureContext as secureOptions by Haraka's tls_socket.
+secureOptions=1073741824